Drug resistance of enteric bacteria. VII. Recombination of R factors with tetracycline-sensitive mutants.
Hashimoto, Hajime (Gunma University, Maebashi, Japan), and Susumu Mitsuhashi. Drug resistance of enteric bacteria. VII. Recombination of R factors with tetracycline-sensitive mutants. J. Bacteriol. 92:1351-1356. 1966.-The transmissible drug-resistance factor R is able to confer resistance to tetracycline (TC), chloramphenicol (CM), streptomycin (SM), and sulfonamide (SA) on a host bacterium when infected by cell-to-cell contact. Tetracycline-sensitive mutants were isolated from either CM- or SM-sensitive mutants of an R factor. Among 30 mutants isolated, 10 were point mutants which could recombine with each other, forming recombinant R factors able to grow on plates containing 50 mug/ml of TC. The recombination frequency of TC-resistant recombinants was 10(-2) to 10(-3) in bacterial cells carrying two types of TC-sensitive R factors by superinfection with both factors. Segregational patterns of the various markers on the R factor, i.e., chl, str, sul, and m, the locus determining R mating, and their linkage order, were investigated among TC-resistant recombinants of the R factor. When TC was used as the selective drug, the tet locus mapped on the R factor as an end marker. In view of the fact that these results are inconsistent with the linkage order of various markers reported previously, a circular genetic structure for the R factor which includes five tet-s and three chl-s loci is presented.
D002874:Chromosome Mapping; D002875:Chromosomes; D004269:DNA, Bacterial; D004352:Drug Resistance, Microbial; D004926:Escherichia coli; D008962:Models, Theoretical; D008967:Molecular Biology; D009154:Mutation; D013752:Tetracycline
D004269:DNA, Bacterial; D013752:Tetracycline